This invention relates to venting reclosable bags, and bag closures constructed to enable evacuation of air from closed bags.
Reclosable bags, such as those employing rib-and-groove type closures, have been known for decades and have become ubiquitous in food packaging. Such zipper-type closures are known to perform reasonably well for sealing bags between uses, and are readily extruded and weldable to various bag film materials.
For many applications, it is desirable prolonged exposure of the bag contents to air be avoided, such as to maintain freshness. Such applications include, for example, food storage bags and bags for marketing such food products as coffee, shredded cheese, fruit and lunchmeat, and also bags for storing fertilizers and seeds, sensitive electronic components, and materials that react with air. In such applications, most of the air within the bag may be expelled by collapsing the bag about its contents prior to closing the sealing closure.
This invention features an improvement in bag and bag closure construction that can enable the evacuation of such bags with the closure closed, without undue complexity and cost.
According to one aspect of the invention, a vented bag includes a bag body having side walls defining a cavity therebetween for holding material therein and having an opening for accessing the cavity, and a reclosable closure secured to the side walls at the bag opening. The closure has extruded male and female interlocking profiles extending along opposing sides of the opening and constructed to releasably interlock along opposite sides of the male profile, and an extruded valve flange laterally spaced apart from the interlocking profiles and extending from one side of the closure to engage an opposing surface of the closure when the profiles are interlocked. The closure defines a vent passage extending from an air space between the opposing sides of the opening and between the interlocking profiles and the valve flange, and the flange and opposing surface are constructed to separate in response to pressure in the cavity for venting the bag with the profiles interlocked, and to increase a contact pressure therebetween in response to presence of a vacuum in the cavity.
In some embodiments the valve flange and one of the interlocking profiles are integrally extruded with a common base member to form one side of the closure. The female interlocking profile may be the one of the interlocking profiles integrally extruded with the common base member and the valve flange, for example, and in some cases the valve flange and opposing surface extend along a full extent of the bag opening.
In some constructions the valve flange and opposing surface are disposed inboard of the interlocking profiles, with the vent passage extending from the air space to atmosphere. In some other constructions the valve flange and opposing surface are disposed outboard of the interlocking profiles, with the vent passage extending from the air space to the cavity.
For some applications the valve flange is resiliently flexed by engagement with the opposing surface when the profiles interlock, to provide an initial contact pressure between the flange and opposing surface.
In a presently preferred embodiment, the valve flange extends as a cantilever from a flange base integrally extruded with one side of the closure, to a distal end having a contact surface configured to seal against said opposing surface, and the flange base is disposed generally inboard of the distal end of the flange, with the profiles interlocked.
In some embodiments the valve flange tapers in thickness, narrowing from its flange base to its distal end, and may be canted away from the cavity of the bag.
In some cases the opposing surface is concave and the contact surface of the valve flange is convex.
In some configurations the interlocking profiles form an airtight seal therebetween when interlocked. In some others, the vent passage is defined between the interlocking profiles, when interlocked.
The vent passage is defined, in some preferred constructions, through resin of one side of the closure. In some other cases the vent passage is defined between a back surface of one side of the closure and an adjacent bag wall material surface. In some cases the vent passage extends through resin of one side of the closure and through adjacent bag film forming one of the bag side walls.
The vented bag may be in the form of a disposable pouch, for example, and the bag opening may extend along an edge of the bag if desired.
In one illustrated embodiment, one of the extruded male and female interlocking profiles is segmented to define the vent passage between longitudinally spaced-apart portions thereof.
In some embodiments, the female interlocking profile has a first side portion, on a side adjacent the valve flange, arranged to engage one side of the male interlocking profile; and a second side portion, on a side opposite the valve flange, arranged to engage another side of the male interlocking profile, with the second side portion having a greater lateral thickness than the first side portion.
According to another aspect of the invention, a closure for bags includes first and second closure strips. The first closure strip has a first elongated base, a first extruded interlocking profile extending from the elongated base, and an extruded valve flange laterally spaced apart from the interlocking profile and extending from the elongated base. The second closure strip has a second elongated base, a second extruded interlocking profile extending from the second elongated base and configured to releasably interlock with the first extruded interlocking profile when pressed together, and a flange contact surface laterally spaced from the second extruded interlocking profile and configured to engage the valve flange of the first closure strip to form an air-tight seal therebetween when the profiles are interlocked, with the closure defining an air space between the interlocked profiles and the valve flange. The closure further defines an air vent passage extending into the air space with the profiles interlocked. The valve flange is constructed to separate from the contact surface in response to pressure on a first side of the valve flange, and to be biased against the contact surface in response to presence of a vacuum on said first side of the valve flange.
In some embodiments, the second extruded interlocking profile defines a groove therein for receiving the first extruded interlocking profile.
Preferably for some applications, the valve flange is constructed and arranged to resiliently flex during engagement with the contact surface when the profiles interlock, to provide an initial contact pressure between the flange and contact surface.
The valve flange may extend as a cantilever, for example, from a flange base integrally extruded with the first elongated base, to a distal end surface configured to seal against the flange contact surface. In some situations, the distal end surface is disposed generally nearer the profiles than is the flange base, with the profiles interlocked.
In some applications, the valve flange is canted toward the first interlocking profile, and the first side of the valve flange may be directed away from the first extruded interlocking profile.
According to another aspect of the invention, a method of filling and evacuating a bag is provided. The method includes providing a bag with a bag body having side walls defining a cavity therebetween for holding material therein and having an opening for accessing the cavity, and a reclosable closure as described herein, secured to the side walls at the bag opening; placing material into the cavity; sealing the bag; and then increasing air pressure within the cavity to expel air from the sealed bag through the vent passage of the closure.
In some cases, increasing air pressure includes compressing opposing sides of the sealed bag to separate the valve flange and contact surface of the closure and push air contained within the cavity out of the bag through the closure. The method also includes, in some cases, after expelling air from the sealed bag, releasing the opposing sides of the bag to re-engage the valve flange and contact surface of the closure and re-seal the bag.
The material may be placed into the cavity through the closure, between the interlocking profiles.
According to another aspect of the invention, a method of forming a reclosable bag is provided. The method includes providing a closure as described herein; attaching the first and second elongated bases to bag film; and forming a bag from the bag film, with the bag defining a cavity for containing contents and the first side of the valve flange directed toward the cavity.
The method also includes, in some instances, forming an air vent passage extending into the air space defined between the interlocked profiles and the valve flange. Forming the air passage may comprise piercing through one of the first and second elongated bases of the closure, for example.
In some other cases, the closure, as provided, defines an air vent passage extending into the air space defined between the interlocked profiles and the valve flange.
Among the potential advantages of several aspects of this invention is the enablement of simple and substantially complete evacuation of already closed storage bags by incorporating a one-way vent structure readily extrudable with many known interlocking profiles.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.